Flexible roll forming method

ABSTRACT

In accordance with an exemplary embodiment of the present invention, a flexible roll forming method for roll forming a beam of a predetermined shape by bending a material fed to a plurality of roll forming units each having upper and lower forming rolls in succession, and for roll forming the beam by feeding the material to a flexible roll forming unit having upper and lower forming rolls disposed on left/right sides of a process direction and both side upper and lower forming rolls disposed to vary positions in a lateral direction of the process and angles from a process direction, respectively, to cause flexible bending of the material in succession over multiple stages, is provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application Nos. 10-2013-0088294, 10-2013-0088297 and 10-2013-0088301 filed in the Korean Intellectual Property Office on Jul. 25, 2013, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION (a) Field of the Invention

The present invention relates to a flexible roll forming method. More particularly, the present invention relates to a flexible roll forming method in which a blank material is flexibly roll formed into a formed beam having modified cross-sections with different widths and heights different along a length direction of the formed beam.

(b) Description of the Related Art

In general, roll forming is a method including uncoiling a coil material and passing it through multi-stages of roll forming units each having one pair of an upper roll and a lower roll disposed on a line for forming a predetermined shape by successive bending. Further, the roll forming method is applicable to fabrication of straight-type formed products formed by bending into predetermined shapes, such as vehicle bumper beams or other members of a certain shape.

FIG. 1 illustrates a schematic view of a related art roll forming system with process steps thereof shown therein.

Referring to FIG. 1, in the related art roll forming method, an uncoiler 1, provided at a start of a process line for uncoiling a coil 10 supplied thereto, processes an uncoiling step S1 of feeding the coil.

A straightener 2 is provided next in a process direction after the uncoiler 1, to process a straightening step S2 for straightening the uncoiled coil 10 from the uncoiler 1 to be flat.

A press 3 is provided next in the process direction after the straightener 2, to process a piercing step S3 for forming holes for various purposes in the coil 10 fed from the straightener 2.

Roll forming units RU1-RU10 of about 10 stages are disposed next in the process direction of the press 3, to process a roll forming step S4 for successively bending the coil 10 being fed thereto through the uncoiler 1, the straightener 2, and the press 3 for roll forming a predetermined straight type of formed beam 20.

A cutting press 4 is provided next in the process direction after the roll forming units, to process a cutting step S5 for cutting the formed beam 20 to produce a formed product 30.

However, in view of the nature of the roll forming with the related art roll forming units, it has a drawback in that only formation of beams having a fixed cross-section along the length direction of the beams is possible, and formation of beams having different widths and heights along the length direction thereof is not possible.

Consequently, since formation of products of different modified cross-sections having different widths and heights along the length direction cannot be formed with the roll forming method, the products have been formed by applying multi-stage forming with a non-continuous process and long cycle time.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a flexible roll forming method applicable to a flexible roll forming system including a flexible roll forming unit for forming a beam having different widths and heights along a length direction from a blank material, a material guiding unit, and a material feeding unit.

In accordance with an exemplary embodiment of the present invention, a flexible roll forming method for roll forming a beam of a predetermined shape by bending a material fed to a plurality of roll forming units each having upper and lower forming rolls in succession, and for roll forming the beam by feeding the material to a flexible roll forming unit having upper and lower forming rolls disposed on left/right sides of a process direction and both side upper and lower forming rolls disposed to vary positions in a lateral direction of the process and angles from a process direction, respectively, to cause flexible bending of the material in succession over multiple stages, is provided.

The material may be a blank with symmetry in a left/right direction with respect to a length direction center line having a width that is varied along the length direction on the whole.

The material may be a blank with symmetry in a left/right direction with respect to a length direction center line having a straight portion with a fixed width, and an expanded portion with a width that becomes larger as the expanded portion goes more in the length direction.

The material may be a blank with symmetry in a left/right direction with respect to a length direction center line having a straight portion with a fixed width, an expanded portion with a width that becomes larger as the expanded portion goes more along the length direction, and a curved portion connecting the straight portion to the expanded portion with a curved line.

The flexible bending may include a step of flexible roll forming the beam having different widths along the length direction and flanges on opposite sides thereof by bending of predetermined widths of opposite edges of the material having different widths along the length direction in succession over multiple stages.

The flexible bending may further include the step of roll forming the beam to have side portions by bending of opposite sides of the beam with respect to the length direction center line along the length direction of the blank in succession over multiple stages.

According to an exemplary embodiment of the present invention, a flexible roll forming method of roll forming a beam of a predetermined shape by bending a material fed to a plurality of roll forming units each having upper and lower forming rolls in succession, and

of roll forming flanges on opposite sides of a blank with symmetry in a left/right direction with respect to a length direction center line, having a straight portion with a fixed width, an expanded portion with a width that becomes larger as the expanded portion goes more in the length direction, and a curved portion connecting the straight portion to the expanded portion with a curved line, with a flexible roll forming unit having upper and lower forming rolls disposed with symmetry in left/right sides of a process direction and both side upper and lower forming rolls disposed to be movable forward/backward in a lateral direction of the process and to vary angles from a process direction, respectively, by bending predetermined widths of opposite edges of the blank with respect to a length direction center line along a length direction of the blank in succession over multiple stages, is provided. Both side upper and lower forming rolls have positions in a lateral direction of the process fixed at the straight portion of the blank, and angles at a right angle to the process direction to form the flanges by roll forming, respectively, the positions in the lateral direction of the process fixed at the curved portion, the angles from the process direction varied up to angles the same as the expanded portion, to form the flanges by roll forming, respectively, and the angles from the process direction at the expanded portion maintained the same as angles of the expanded portion, and the positions in the lateral direction of the process which become larger as the expanded portion goes along the length direction of the blank to form the flanges on the opposite sides, to cause flexible roll forming of the formed beam having different widths along the length direction.

The flexible roll forming may further include the step of roll forming the formed beam to have rectangular side portions by bending opposite sides of the formed beam with respect to the length direction center line along the length direction of the blank in succession over multiple stages.

According to an exemplary embodiment of the present invention, in a flexible roll forming method of roll forming a beam of a predetermined shape by bending a material fed to a plurality of roll forming units each having upper and lower forming rolls in succession, the flexible roll forming method includes:

a first step of roll forming flanges on opposite sides of a blank with symmetry in a left/right direction with respect to a length direction center line, having a straight portion with a fixed width, an expanded portion with a width that becomes larger as the expanded portion goes more in the length direction, and a curved portion connecting the straight portion to the expanded portion with a curved line, with a flexible roll forming unit having upper and lower forming rolls disposed with symmetry in left/right sides of a process direction and both side upper and lower forming rolls disposed to be movable forward/backward in a lateral direction of the process and to vary angles from a process direction, respectively, by bending predetermined widths of opposite edges of the blank with respect to a length direction center line along a length direction of the blank in succession over multiple stages. Both side upper and lower forming rolls have positions in a lateral direction of the process fixed at the straight portion of the blank, and angles at a right angle to the process direction to form the flanges by roll forming, respectively, the positions in the lateral direction of the process fixed at the curved portion, the angles from the process direction varied up to angles the same as the expanded portion, to form the flanges by roll forming, respectively, and the angles from the process direction at the expanded portion maintained the same as angles of the expanded portion, and the positions in the lateral direction of the process which become larger as the expanded portion goes in along the length direction of the blank to form the flanges on the opposite sides, to cause flexible roll forming of the formed beam having different widths along the length direction; and

a second step of roll forming the beam to have rectangular side portions by bending of opposite sides of the formed beam with respect to the length direction center line along a length direction of the blank in succession over multiple stages after the first step, wherein, in a final step of the first step, the roll forming occurs in a state in which the upper and lower forming rolls are in rolling contact with a reference surface of the blank and respective surfaces of the flanges at the same time.

The flexible roll forming method in accordance with an exemplary embodiment of the present invention can cause flexible roll forming of a 3D formed product B3 having a modified cross-section with different widths and heights along the length direction by using the blank material having the straight portion P1, the expanded portion P2, and so on by arranging the multi-stage flexible roll forming unit to vary the positions and the angles in the lateral direction of the process of the upper and lower forming rolls R1 and R2.

With such formed products, vehicle body members, frames, and beams having cross-sectional profiles of which widths and heights are different from one another along the length direction can be roll formed as one unit with one roll forming event, permitting minimization of following post, such as welding, jointing, and the like, and contributing to manufacture of lighter vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view of a related art roll forming system, with steps thereof shown thereon.

FIG. 2 illustrates a perspective view of a flexible roll forming unit to which a flexible roll forming method in accordance with an exemplary embodiment of the present invention is applicable.

FIG. 3 illustrates a partial exploded perspective view of a flexible roll forming unit to which a flexible roll forming method in accordance with an exemplary embodiment of the present invention is applicable.

FIG. 4 illustrates a perspective view of another flexible roll forming unit to which a flexible roll forming method in accordance with an exemplary embodiment of the present invention is applicable.

FIG. 5 illustrates an exploded perspective view of forward/backward moving means and turning means in another flexible roll forming unit to which a flexible roll forming method in accordance with an exemplary embodiment of the present invention is applicable.

FIG. 6 illustrates a partial exploded perspective view of roll forming means in another flexible roll forming unit to which a flexible roll forming method in accordance with an exemplary embodiment of the present invention is applicable.

FIGS. 7 to 11 illustrate schematic views each showing a step of a flexible roll forming method in accordance with an exemplary embodiment of the present invention.

DESCRIPTION OF SYMBOLS

-   -   S1, S2: first and second steps     -   B1: blank     -   B2: formed beam     -   B3: formed product     -   F: reference surface     -   F1: flange     -   F2: side     -   R1: upper forming roll     -   R2: lower forming roll     -   P1: straight portion     -   P2: expanded portion     -   P3: curved portion

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

A thickness or a size of an element shown in a drawing can be exaggerated, omitted, or shown schematically for convenience or clarity of description.

Parts not relevant to the description are omitted for clarity of the description of an exemplary embodiment of the present invention, and the same or similar elements will be given identical reference numerals throughout the specification.

FIG. 2 illustrates a perspective view and FIG. 3 illustrates a partial exploded perspective view of a flexible roll forming unit to which a flexible roll forming method in accordance with an exemplary embodiment of the present invention is applicable.

A flexible roll forming unit 100 in accordance with an exemplary embodiment of the present invention includes a base 103 symmetrically disposed on both sides of a center line LS of a process direction, with forward/backward moving means 110, turning means 120, and roll forming means 130 mounted thereon.

Each of the bases 103 has a space portion 105 formed therein, and an upper side opening 105 a formed therein connected to the space portion 105.

The base 103 has rails 107 mounted on an upper side of both sides of the opening 105 a in a lateral direction of a process.

The forward/backward moving means 110 includes a slide plate 111 movably provided along the rails 107 on the base 103.

The slide plate 111 is mounted on the rails 107 on the base 103 through a slider 112 to be movable in the lateral direction of the process.

A forward/backward moving cylinder 113 connected to the slide plate 111 with an operation rod 114 is mounted to one side of the base 103. If the forward/backward moving cylinder 113 moves forward or backward, the slide plate 111 moves in the lateral direction of the process.

The turning means 120 includes a turning reducer 123 mounted to a center of the slide plate 111, and a turning motor 122 mounted under the slide plate 111 connected to the turning reducer 123.

In this case, the turning motor 122 may be a servo motor which is reversible, and of which RPM and number of rotations are controllable.

The turning reducer 123 has a reducer shaft 124 having a turntable 121 mounted thereto for rotating the turntable 121 with a torque of the turning motor 122 transmitted through the turning reducer 123 at a reduced speed.

The turning motor 122 is disposed in the space portion 105 through the opening 105 a in the base 103 for moving without interference with the base 103 when the slide plate 111 slidably moves in the lateral direction of the process of the base 103.

A sensing dog 126 is mounted on an underside of the turntable 121, and a plurality of sensors 125 for sensing the sensing dog 126 are mounted on the slide plate 111 at the turntable 121 to sense a home position and states of rotation limit positions of the turntable 121 in each direction with respect to the slide plate 111, and to forward a signal thereof to a controller (not shown).

In this case, although the sensor 125 may be a proximity sensor for sensing the sensing dog 126 when the sensing dog 126 comes within a predetermined range, the sensor 125 is not limited to this, and other sensing means such as a limit switch are applicable as long as the sensing means can sense a rotated position of the turntable 121 on the slide plate 111.

The roll forming means 130 is mounted on the turntable 121 and includes a plurality of roll posts 131, upper and lower roll housings RH1 and RH2, upper and lower roll motors RM1 and RM2, upper and lower forming rolls R1 and R2, and adjusting bolts 132.

The roll posts 131 are coupled to upper and lower plates 133 and 134 with bolts, and fixedly secured to the turntable 121 through the lower plate 134.

The upper and lower roll housings RH1 and RH2 are mounted to both sides of the roll posts 131 to be movable in up/down directions.

Upper and lower reducers 135 and 136 are mounted to one side of the upper and lower roll housings RH1 and RH2, respectively, and upper and lower roll motors RM1 and RM2 connected to the upper and lower reducers 135 and 136, respectively.

Roll shafts 137 are rotatably mounted to the upper and lower roll housings RH1 and RH2, respectively, the roll shafts 137 are respectively connected to the upper and lower reducers 135 and 136, and the upper and lower forming rolls R1 and R2 are respectively mounted to the roll shafts 137.

That is, the upper and lower forming rolls R1 and R2 are respectively coupled to the roll shafts 137 while being secured with keys, and blanking plates 138 are fastened to fore ends of the roll shafts 137 for preventing the upper and lower forming rolls from falling off, respectively.

In this case, the upper and lower roll motors RM1 and RM2 may be servo motors which are reversible and of which RPM and number of rotations are controllable.

The adjusting bolts 132 are provided between the upper plate 133 and the upper roll housing RH1 and between the lower plate 134 and the lower housing RH2 for adjusting and securing positions of the upper and lower roll housings RH1 and RH2, respectively.

Each of the adjusting bolts 132 has a fixing nut 139 fastened thereto for fixing the upper and lower roll housings RH1 and RH2 in the adjusted positions, respectively.

FIG. 4 illustrates a perspective view of another flexible roll forming unit to which a flexible roll forming method in accordance with an exemplary embodiment of the present invention is applicable, FIG. 5 illustrates an exploded perspective view of forward/backward moving means and turning means in another flexible roll forming unit to which a flexible roll forming method in accordance with an exemplary embodiment of the present invention is applicable, and FIG. 6 illustrates a partial exploded perspective view of roll forming means in another flexible roll forming unit to which a flexible roll forming method in accordance with an exemplary embodiment of the present invention is applicable.

In describing configurations of the flexible roll forming units in FIGS. 4 to 6, for convenience of understanding, parts that are the same or similar to the flexible roll forming unit shown in FIGS. 2 to 3 will be given the same or similar reference numerals.

The flexible roll forming unit 100 in accordance with an exemplary embodiment of the present invention includes bases 103 symmetrically disposed on both sides of a process direction center line LS with respect to a left/right direction, respectively, and forward/backward moving means 110, turning means 120, and roll forming means 130 mounted on each of the bases 103.

Each of the bases 103 has a space portion 105 formed therein, and an upper side opening 105 a formed therein connected to the space portion 105.

The base 103 has rails 107 mounted on an upper side of both sides of the opening 105 a in a lateral direction of a process.

The forward/backward moving means 110 includes a slide plate 111 movably provided along the rails 107 on the base 103.

The slide plate 111 is mounted on the rails 107 on the base 103 through a slider 112 to be movable in the lateral direction of the process.

A forward/backward moving cylinder 113 connected to the slide plate 111 with an operation rod 114 is mounted to one side of the base 103. If the forward/backward moving cylinder 113 moves forward or backward, the slide plate 111 moves in the lateral direction of the process.

The turning means 120 includes a turning reducer 123 mounted to a center of the slide plate 111 and a turning motor 122 mounted under the slide plate 111 connected to the turning reducer 123.

In this case, the turning motor 122 may be a servo-motor which is reversible, and of which RPM and number of rotations are controllable.

The turning reducer 123 has a reducer shaft 124 having a turn-table mounted to an upper side thereof for rotating the turn table 121 with a torque of the turning motor 122 transmitted through the turning reducer 123 at a reduced speed.

The turning motor 122 is disposed in the space portion 105 through the opening 105 a in the base 103 for moving without interference with the base 102 when the slide plate 111 slidably moves in the lateral direction of the process of the base 103.

A sensing dog 126 is mounted on an underside of the turntable 121, and a plurality of sensors 125 for sensing the sensing dog 126 are mounted on the slide plate 111 at the turntable 121 to sense a home position and states of rotation limit positions of the turntable 121 in each direction with respect to the slide plate 111, and to forward a signal thereof to a controller (not shown).

In this case, the sensor 125 may be a proximity sensor for sensing the sensing dog 126 when the sensing dog 126 comes within a predetermined range, but the sensor 125 is not limited to this, and other sensing means such as a limit switch are applicable as long as the sensing means can sense a rotation position of the turn table 121 on the slide plate 111.

The roll forming means 130 is mounted on the turntable 121, for flexible roll forming of a material fed thereto as the upper and lower forming rolls R1 and R2 respectively mounted to the upper and lower roll housings RH1 and RH2 are rotated by one roll motor RM, while at the same time, varying positions and angles of the upper and lower forming rolls R1 and R2 by using the forward/backward moving means 110 and the turning means 120.

The roll forming means 130 includes a plurality of roll posts 131, upper and lower roll housings RH1 and RH2, a roll motor RM, upper and lower forming rolls R1 and R2, and adjusting bolts 132.

The roll posts 131 are coupled to the upper and lower plates 133 and 134 with bolts, and fixedly secured to the turn table 121 through the lower plate 134.

The upper and lower roll housings RH1 and RH2 are mounted on both sides of the roll posts 131 to be movable in up/down directions.

A roll reducer 136 is mounted to one side of the lower roll housing RH2, and the roll motor RM is connected to the roll reducer 136.

A roll shaft 137 is rotatably mounted to the lower roll housing RH2 passed therethrough, the roll shaft 137 is connected to the roll reducer 136, and the lower forming roll R2 is mounted to the roll shaft 137.

That is, the lower forming roll R2 is coupled to the roll shaft 137 secured with a key, and a blanking plate 138 is fastened to a fore end of the roll shaft 137 for preventing the lower forming roll from falling off.

In this case, the roll motor RM may be a servo motor which is reversible and of which RPM and number of rotations are controllable.

The upper forming roll R1 is rotatably mounted to a rotation bracket 157 secured to the upper roll housing R1 with a tilted shaft 141, and the upper forming roll R1 has a forming surface 143 facing an outside surface and an outside circumferential surface of the lower forming roll R2.

The rotation bracket 157 is mounted to the upper roll housing RH1 in a tilted position with a plurality of mounting rods 145 with bolts 151, mounting bolts 147 respectively mounted to the mounting rods 145, and one center pin 149 fastened with a pin bolt 153 and then inserted in a pinhole in the upper roll housing RH1.

The adjusting bolts 132 are provided between the upper plate 133 and the upper roll housing RH1 and between the lower plate 134 and the lower housing RH2 for adjusting and securing positions of the upper and lower roll housings RH1 and RH2, respectively.

In this case, each of the adjusting bolts 132 has a fixing nut 139 fastened thereto for fixing the upper and lower roll housings RH1 and RH2 to the adjusted positions, respectively.

Eventually, the flexible roll forming unit 100 described thus causes flexible roll forming of a material fed thereto as the upper and lower forming rolls R1 and R2 are rotated by the roll motor RM, while at the same time, varying positions in the lateral direction of the process and angles from the process direction of the upper and lower forming rolls R1 and R2 by operating the forward/backward moving means 110 and the turning means 120.

FIGS. 7 to 11 illustrate schematic views each showing a step of a flexible roll forming method in accordance with an exemplary embodiment of the present invention.

Referring to FIGS. 2 to 11, basically, the flexible roll forming method in accordance with an exemplary embodiment of the present invention uses a blank B1, rather than a coil, as the material.

The flexible roll forming method has the same basic concept as the related art, in which a material is fed through roll forming units of at least 10 stages each having an upper forming roll R1 and a lower forming roll R2 for bending of the material in succession to cause roll forming of the material into a formed beam of a predetermined shape.

However, the roll forming unit shown in FIG. 2 or 4 may be applied to the flexible roll forming method in accordance with an exemplary embodiment of the present invention instead of the related art roll forming unit.

Basically, the material used in the flexible roll forming method in accordance with an exemplary embodiment of the present invention is a blank B1 of a predetermined standard. It is favorable for the blank to be symmetric in a left/right direction with respect to a length direction center line S taking formability into account.

Although forming is difficult if the blank B1 has a large variation of a width along a length direction, the blank B1 may have a width that varies along the length direction on the whole, and may include a straight portion P1 having a fixed width along the length direction, an expanded portion P2 having a width which becomes larger farther in the length direction, and a curve portion P3 connecting the straight portion P1 to the expanded portion P2 with a curved line.

In this case, the expanded portion P2 may be defined as a narrow portion having a width which becomes smaller depending on a forming direction. In the flexible roll forming method in accordance with an exemplary embodiment of the present invention, the narrow portion has the same concept as the expanded portion P2, but it is understood to have an opposite concept depending on the forming direction.

Hereafter, the flexible roll forming method in accordance with an exemplary embodiment of the present invention applicable to the flexible roll forming unit will be described.

That is, basically, the flexible roll forming method in accordance with an exemplary embodiment of the present invention may include a first step S1 and a second step S2.

The first step S1 is a step in which edges of the blank B1 opposite with respect to the length direction center line S are bent along the length direction of the blank in succession over multiple stages to form a formed beam B2 having flanges F1.

The second step S2 is a step after the first step S1, in which the opposite sides of the blank with respect to the length direction center line S of the blank are bent along the length direction of the blank in succession over multiple stages to form a formed product B3 having opposite side portions F2, such as a vehicle body member of a particular shape.

First, in the first step S1, the upper and lower forming rolls R1 and R2 are disposed to opposite sides in symmetry in a left/right direction such that the roll forming can occur in a state that the upper and lower forming rolls R1 and R2 are in rolling contact with the opposite edges of the blank B1 with respect to the length direction center line S of the blank B1 along the length direction thereof.

Referring to FIGS. 7 and 8, the first step includes the step S11 of feeding the blank B1, having a straight portion P1 with a fixed width along a length direction, an expanded portion P2 with a width which becomes larger as the expanded portion P2 goes farther in the length direction, and a curved portion P3 which connects the straight portion P1 to the expanded portion P2 with a curved line, to a flexible roll forming unit to bend opposite edges of the blank B1 with respect to the length direction center line S along the length direction of the blank B1 in a state in which fixed widths of the opposite edges with respect to a length direction center line are in rolling contact with the upper and lower forming rolls R1 and R2 to cause roll forming of the opposite edges into flanges F1 over multiple stages along the length direction of the blank.

After the step S11 of roll forming the flanges F1, a final stage flexible roll forming unit in the first step S1 roll forms in a state in which the opposite upper and lower forming rolls R1 and R2 are in rolling contact with the reference surface F of the blank B1 and respective surfaces of the flanges F1 at the same time, to form the flanges F1 at a right angle with respect to the reference surface F of the blank B1 (S12).

In this case, the roll forming in a state in which the opposite side upper and lower forming rolls R1 and R2 are in rolling contact with the reference surface F of the blank B1 and respective surfaces of the flanges F1 at the same time is done for preventing distortion of the material when only the flanges F1 are supported by the rolls to form the flanges F1 close to a right angle with respect to the reference surface F of the blank B1.

In the second step, the upper and lower forming rolls R1 and R2 are disposed in symmetry with respect to the left/right direction so as to be in rolling contact with the blank B1 at opposite sides thereof with respect to the length direction center line S.

In this case, in the second step S2, although the upper and lower forming rolls R1 and R2 are not required to vary positions thereof in the process direction and angles thereof from the lateral direction of the process, they may be required to be variable for meeting a case of a specification change of the product.

That is, referring to FIGS. 7 and 8, in the second step S2, the blank B1 having the opposite edges with respect to the length direction center line S flexible roll formed into the flanges F1 in the first step S1 is roll formed in a state in which the upper and lower forming rolls R1 and R2 are in rolling contact with opposite sides with respect to the length direction center line S, to bend the blank B1 in an opposite direction of the flanges F1 (S21).

In a final step of the second step S2, the upper and lower forming rolls R1 and R2 form opposite sides F2 which are at a right angle with respect to the reference surface F of the blank B1 (S22).

Referring to FIGS. 9 and 10, the first step S1 at each stage will be described based on the blank B1 having the straight portion P1, the expanded portion P2, and the curved portion P3.

Referring to FIG. 9 (a), in the step for roll forming the flanges F1 at the straight portion P1 of the blank B1, the opposite upper and lower forming rolls R1 and R2 are disposed to have fixed positions in the lateral direction of the process, and angles at a right angle to the process direction at the straight portion P1 of the blank B1 for bending fixed widths of the edges of the straight portion P1 downward to make roll forming of the flanges F1, respectively.

Then, referring to FIG. 9 (b), the opposite upper and lower forming rolls R1 and R2 proceed to the curved portion P3 of the blank B1 while having the fixed positions in the lateral direction of the process as they were, and only varying the angles from the process direction up to an angle 8 the same as the expanded portion P2 by driving the motor to cause roll forming of the fixed widths of the edges of the curved portion P3 into the flanges F1.

Thereafter, referring to FIG. 9 (c), the opposite upper and lower forming rolls R1 and R2 proceed to the expanded portion P2 of the blank B1, and maintain the angles in the process direction the same as the angle 8 of the expanded portion P2 as they were, while moving the positions P in the lateral direction of the process outward according to the edges of the expanded portion P2 by driving a cylinder, to cause roll forming of the fixed widths of the opposite edges of the expanded portion P2 into the flanges F1, and to form a formed beam B2 having different widths along the length direction and the flanges F1 by flexible roll forming.

Referring to FIG. 10, in a final step of the first step S1, the roll forming is progressed in a state in which shapes of the upper and lower forming rolls R1 and R2 are changed such that the opposite upper and lower forming rolls R1 and R2 are in rolling contact with the reference surface F of the blank B1 and the respective surfaces of the flanges F1 at the same time. For example, the flexible roll forming unit shown in FIG. 4 may be used.

As described before, this is for preventing the distortion of the material in the course of forming from occurring when only the flanges F1 are supported by the rolls, resulting in forming the flanges F1 close to a right angle with respect to the reference surface F of the blank B1.

FIG. 11 illustrates a perspective view of the second step in the flexible roll forming method in accordance with an exemplary embodiment of the present invention.

Referring to FIG. 11, the second step S2 will be described, in which the rectangular opposite sides F2 with respect to the length direction center line S of the formed beam B2 having the opposite rectangular flanges F1 are formed.

As described above, the second step S2 progresses after the first step S1, in which roll forming of the rectangular opposite sides F2 is performed by bending opposite sides of the formed beam B2 with respect to the length direction center line S along the length direction of the blank in succession over multiple stages.

Referring to FIG. 11, the second step S2 progresses in a state in which the upper and lower forming rolls R1 and R2 are disposed in symmetry in an opposite left/right direction so as to be in rolling contact with the blank B1 on opposite sides of the length direction center line S.

The second step is progressed by bending opposite sides of the formed beam B2 having the opposite flanges F1 with reference to the length direction center line S of the formed beam B2 in an opposite direction of the flanges F1 over multiple stages, respectively.

Referring to FIG. 7, by the second step S2, the flanges F1 are disposed parallel with the reference surface F of the blank B1, and the opposite sides F2 form a right angle with respect to the flanges F1 and the reference surface F of the blank B1.

In this case, the flexible roll forming unit shown in FIG. 2 maybe used.

In this case, the first step S1 and the second step S2 are progressed with identical steps, with only a difference of forming depths, by the flexible multi-stage roll forming unit.

Thus, the flexible roll forming method in accordance with an exemplary embodiment of the present invention can cause flexible roll forming of a 3D formed product B3 having a modified cross-section with different widths and heights along the length direction by using the blank material having the straight portion P1, the expanded portion P2, and so on by arranging the multi-stage flexible roll forming unit to vary the positions and the angles in the lateral direction of the process of the upper and lower forming rolls R1 and R2.

With such formed products B3, vehicle body members, frames, and beams having cross-sectional profiles of which widths and heights are different from one another along the length direction can be roll formed as one unit with one roll forming event, permitting minimizing of following steps, such as welding, jointing, and the like, and also contributing to manufacture of lighter vehicles.

Although one exemplary embodiment of the present invention is described, the present invention is not limited to the exemplary embodiment, but includes all ranges of changes made by a person skilled in this field of art from the exemplary embodiment of the present invention and recognized equivalents of the exemplary embodiment.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be 1.0 understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

What is claimed is:
 1. A flexible roll forming method for roll forming a beam of a predetermined shape by bending a material fed to a plurality of roll forming units each having upper and lower forming rolls in succession, and for roll forming the beam by feeding the material to a flexible roll forming unit having upper and lower forming rolls disposed on left/right sides of a process direction and both side upper and lower forming rolls disposed to vary positions in a lateral direction of the process and angles from a process direction, respectively, to cause flexible bending of the material in succession over multiple stages.
 2. The flexible roll forming method of claim 1, wherein the material is a blank with symmetry in a left/right direction with respect to a length direction center line having a width that is varied along the length direction on the whole.
 3. The flexible roll forming method of claim 1, wherein the material is a blank with symmetry in a left/right direction with respect to a length direction center line having a straight portion with a fixed width, and an expanded portion with a width that becomes larger as the expanded portion goes more in the length direction.
 4. The flexible roll forming method of claim 1, wherein the material is a blank with symmetry in a left/right direction with respect to a length direction center line having a straight portion with a fixed width, an expanded portion with a width that becomes larger as the expanded portion goes more along the length direction, and a curved portion connecting the straight portion to the expanded portion with a curved line.
 5. The flexible roll forming method of claim 1, wherein the flexible bending includes a step of flexible roll forming the beam having different widths along the length direction and flanges on opposite sides thereof by bending of predetermined widths of opposite edges of the material having different widths along the length direction in succession over multiple stages.
 6. The flexible roll forming method of claim 5, wherein the flexible bending further includes the step of roll forming the beam to have side portions by bending of opposite sides of the beam with respect to the length direction center line along the length direction of the blank in succession over multiple stages.
 7. A flexible roll forming method of roll forming a beam of a predetermined shape by bending a material fed to a plurality of roll forming units each having upper and lower forming rolls in succession, and of roll forming flanges on opposite sides of a blank with symmetry in a left/right direction with respect to a length direction center line, having a straight portion with a fixed width, an expanded portion with a width that becomes larger as the expanded portion goes more in the length direction, and a curved portion connecting the straight portion to the expanded portion with a curved line, with a flexible roll forming unit having upper and lower forming rolls disposed with symmetry in left/right sides of a process direction and both side upper and lower forming rolls disposed to be movable forward/backward in a lateral direction of the process and to vary angles from a process direction, respectively, by bending predetermined widths of opposite edges of the blank with respect to a length direction center line along a length direction of the blank in succession over multiple stages, wherein both side upper and lower forming rolls have positions in a lateral direction of the process fixed at the straight portion of the blank, and angles at a right angle to the process direction to form the flanges by roll forming, respectively, the positions in the lateral direction of the process fixed at the curved portion, the angles from the process direction varied up to angles the same as the expanded portion, to form the flanges by roll forming, respectively, and the angles from the process direction at the expanded portion maintained the same as angles of the expanded portion, and the positions in the lateral direction of the process which become larger as the expanded portion goes along the length direction of the blank to form the flanges on the opposite sides, to cause flexible roll forming of the formed beam having different widths along the length direction.
 8. The flexible roll forming method of claim 7, wherein the flexible roll forming further includes the step of making roll forming the formed beam to have rectangular side portions by bending opposite sides of the formed beam with respect to the length direction center line along the length direction of the blank in succession over multiple stages.
 9. A flexible roll forming method of roll forming a beam of a predetermined shape by bending a material fed to a plurality of roll forming units each having upper and lower forming rolls in succession, the flexible roll forming method comprising: a first step of roll forming flanges on opposite sides of a blank with symmetry in a left/right direction with respect to a length direction center line, having a straight portion with a fixed width, an expanded portion with a width that becomes larger as the expanded portion goes more in the length direction, and a curved portion connecting the straight portion to the expanded portion with a curved line, with a flexible roll forming unit having upper and lower forming rolls disposed with symmetry in left/right sides of a process direction and both side upper and lower forming rolls disposed to be movable forward/backward in a lateral direction of the process and to vary angles from a process direction, respectively, by bending predetermined widths of opposite edges of the blank with respect to a length direction center line along a length direction of the blank in succession over multiple stages, wherein both side upper and lower forming rolls have positions in a lateral direction of the process fixed at the straight portion of the blank, and angles at a right angle to the process direction to form the flanges by roll forming, respectively, the positions in the lateral direction of the process fixed at the curved portion, the angles from the process direction varied up to angles the same as the expanded portion, to form the flanges by roll forming, respectively, and the angles from the process direction at the expanded portion maintained the same as angles of the expanded portion, and the positions in the lateral direction of the process which become larger as the expanded portion goes in along the length direction of the blank to form the flanges on the opposite sides, to cause flexible roll forming of the formed beam having widths different along the length direction; and a second step of roll forming the beam to have rectangular side portions by bending of opposite sides of the formed beam with respect to the length direction center line along a length direction of the blank in succession over multiple stages after the first step, wherein, in a final step of the first step, the roll forming occurs in a state in which the upper and lower forming rolls are in rolling contact with a reference surface of the blank and respective surfaces of the flanges at the same time. 